Thread: OT: Concrete grinding

If one wants to resurface a concrete wall, how is it done?

The poured walls in our old shop would snag you if you brushed against them. We took a big right angle grinder with a wheel made for concrete and knocked off the upstanding parts.

You don't say what you are trying to accomplish. Is it just rough, is it deteriorating, do you just want a better surface?????
As stated, you could hit it with a grinder. Or apply a bonding agent and a skim coat of masonry or stucco.
Need more info.

Originally Posted by Timw

You don't say what you are trying to accomplish. Is it just rough, is it deteriorating, do you just want a better surface?????
As stated, you could hit it with a grinder. Or apply a bonding agent and a skim coat of masonry or stucco.
Need more info.

Looking to remove 3/4 - 1 inch from the entire surface area of the wall.

Well, unless you hire a sculptor, the mechanics of the job will be to turn XXXX cubic inches of concrete into dust. If you or your tools have to simultaneously occupy the space, control of the dust is going to be the key issue. If you can have it done "wet", you'll be ahead of the game a little. Scoring then breaking out chunks will help some, but there will still be a manual finishing step unless you A: like the look, and B: keep your score lines very regular... as in cut with a guided saw.

We're all waiting to hear the reason, you know...

Chip

Originally Posted by Chip Chester

[snip]

We're all waiting to hear the reason, you know...

Chip

Come on now, Chip. Isn't it more fun to just wildly speculate on what Spud has and what he is trying to accomplish? Kinda' like the PM version of Twenty Questions!

Steve

Originally Posted by Chip Chester

Well, unless you hire a sculptor, the mechanics of the job will be to turn XXXX cubic inches of concrete into dust. If you or your tools have to simultaneously occupy the space, control of the dust is going to be the key issue. If you can have it done "wet", you'll be ahead of the game a little. Scoring then breaking out chunks will help some, but there will still be a manual finishing step unless you A: like the look, and B: keep your score lines very regular... as in cut with a guided saw.

We're all waiting to hear the reason, you know...

Chip

Probably wants a bigger shop!

I have visited a few poured concrete houses which have internally polished walls and floors. There are specialised wet grinding machines to do this, but that is all I know.

I seriously doubt you are going to take 3/4 inch or more off the wall surface, unless you hire a professional who does that.

I have NO idea WHY you want to do that. If your walls were simply rough from being poured, bubbles and parting lines from the forms, I could see it.

George

Removing 3/4" + from a concrete wall is going to be a herculean effort. Firstly your going to have to score it with cutting wheels to get your near desired depth, break that out then grind it as flat as you want. Would almost guaranteed be faster to demolish + pour a new wall. Grinding 1/16" off any real area would take a long time. For get doing it dry, heat would be a issue, gotta be done wet.

Originally Posted by Spud

Looking to remove 3/4 - 1 inch from the entire surface area of the wall.

Originally Posted by technocrat

Probably wants a bigger shop!...

No disrespect to Spud, but you gotta appreciate that response!!

The walls are not load bearing, they are 2 brick courses wide and about .5 - .75 inches thick concrete plaster on either side. The concrete is not uniform color, and many areas show up as patchy . In addition some areas are smooth and some not, and one wall is thicker than the rest.
I was thinking , best to remove most of the conrete plaster coating and apply fresh coating, would be best way to achieve uniform color .

Originally Posted by Spud

The walls are not load bearing, they are 2 brick courses wide and about .5 - .75 inches thick concrete plaster on either side. The concrete is not uniform color, and many areas show up as patchy . In addition some areas are smooth and some not, and one wall is thicker than the rest.
I was thinking , best to remove most of the conrete plaster coating and apply fresh coating, would be best way to achieve uniform color .

If it is discolored and/or bulging from deterioration - moisture intrusion etc - then perhaps so. AND finding and correcting the source of whatever has been damaging it.

If the plaster and its adhesion are structurally sound and 'chemically' stable, OTOH .. and no ongoing source of damage is involved, then sealing and skimming level and colorizing or coating - even a hard glassy glaze - to suit is less messy yet. AND places zero stress on the brickwork.

Removing a plaster coat, whether gypsum or portland-cement based parging is child's play compared to cutting into monolithic concrete, and done all the time without all that much dust .. by those in that trade.

Either way - I'd look for a professional at such things who is involved every day in such treatments.
It is a different discipline from gnawing on metal, and I'd expect those who work at it to know their trade as well as we know ours.

References from satisfied customers are a good idea, of course, as there are also more than a few mere mud-slappers who do NOT 'have the knowledge'.

Bill

Yup, what Bill sez. Chipping a layer of something off brick is mucho easier than the original project as described. For references, check contractors that convert lofts, etc. to living spaces. They will be well-versed in re-exposing brick walls. Re-coating or painting should be no trouble after the removal.

Chip

Originally Posted by Chip Chester

Yup, what Bill sez. Chipping a layer of something off brick is mucho easier than the original project as described. For references, check contractors that convert lofts, etc. to living spaces. They will be well-versed in re-exposing brick walls. Re-coating or painting should be no trouble after the removal.

Chip

Think Hong Kong. Essentially 100% of residential housing is concrete for fire, fungus, rot, and insect resistance.

'State Bird' is the Tower Crane, and National Anthem is the unceasing sound of electric chipping hammers prepping for new tile, wire, or plumbing, changed nearly every time a tenant moves-out.

Maddening that wiring is buried directly into the concrete rather than a few cents worth of even plastic garden-hose used for pull-and-replace conduit, but .. there you have it. Wallpaper turns brown and phenolic stink pervades from undersized wire, one calls for the chippies and tries yet-another time. 'muddy legs' the 'lectrical guru for the week not wanting to know that a spec of 'x' milllimeter should be applied to the conductor, not the outer jacket...

:-(

Bill

Spud,

If you have a 2-wythe brick wall which has been parged with cement plaster and it is irregular, loose, etc., the easiest way to remove the plaster and make it uniform is to rent a 20# pneumatic hammer fitted with a bush hammer tool. The head of this tool is either round or square and looks like a meat tenderizer. You can apply light or heavy pressure during use and it will 'eat' the plaster. You can periodically wet the area being hammered or have someone direct a fine water mist as you proceed and the dust will be manageable.

Once you have removed/evened the surface to your satisfaction, you can apply a fresh cement plaster coat. If I were you, unless you have experience with this task, I would hire someone who is accustomed to doing stucco or plaster work, as he will make it look far simpler than it actually is. Typically, when cement plaster is applied, it is done with a trowell that looks like a cement finisher's tool and it is periodically smoothed with a darby that is 3-4' long and acts as a float to make the surface more uniform and smooth. The process is much like finishing a concrete floor except that the trowell preceeds the float. The darby is actually more like a very long finishing trowell with two handles for control. I have watched good craftsmen do this and it is a pleasure to see and to see the results. This is the process they use to install hard plaster finishes on interior walls but, since the cost is high, it is only found in high-end homes in certain parts of the country today.

Edit: The hammer will likely be 30# -40# and considered a chipping hammer if you go to a rental house to find one.

We call it render over here, oftern used as a base for plaster. Removing that is easy compared to refacing a concrete wall.

A wall ain't a concrete wall if its made of bricks either. Bit like aluminium is not billet if its from a extruded section. Not as cast lump

Originally Posted by adama

We call it render over here, oftern used as a base for plaster. Removing that is easy compared to refacing a concrete wall.

A wall ain't a concrete wall if its made of bricks either. Bit like aluminium is not billet if its from a extruded section. Not as cast lump

More like aluminium is not billet if it is bronze powder.

A BRICK wall is none to happy with successive impact/hammer loads at right angles to its height. More better to use the light electric or air tool and a blade one can get UNDER the parging or plaster with. Impacts should be fast but light, and almost parallel to the horizontal axis of the wall. Unwanted material comes off in slivers about the size and shape of one's hand (on average). Much less load on the brick and its mortar. Good time to re-point the brick once exposed if need be . Use type 'S' mortar for best strength.

Go at it face-on attempting to spall off unwanted material with a 30# or 40# hammer?

One may have a collapsed pile of bricks where the wall once stood. Pray that it was not a load-bearing wall...

Bill

Originally Posted by thermite

More like aluminium is not billet if it is bronze powder.

A BRICK wall is none to happy with successive impact/hammer loads at right angles to its height. More better to use the light electric or air tool and a blade one can get UNDER the parging or plaster with. Impacts should be fast but light, and almost parallel to the horizontal axis of the wall. Unwanted material comes off in slivers about the size and shape of one's hand (on average). Much less load on the brick and its mortar. Good time to re-point the brick once exposed if need be . Use type 'S' mortar for best strength.

Go at it face-on attempting to spall off unwanted material with a 30# or 40# hammer?

One may have a collapsed pile of bricks where the wall once stood. Pray that it was not a load-bearing wall...

Bill

Bill, with all due respect you don't know what you are talking about. Have you ever seen a bush hammer? If you had, you would understand how it works. The impact frequency is high and you don't apply your entire body weight to the tool. The weight of the hammer makes it more stable and easier to manage as it absorbs the rebound from the tool. It works much like a needle scaler except that it is one piece with pyramid-shaped projections about 3/8" high across the face of the tool. I simply pulverizes the surface to which it is applied and the area of the face spreads the impact so that it does not do structural damage. Of course if the wall is flimsy and weak, then this is probably not a good solution.

Originally Posted by Carl Douglass

Bill, with all due respect you don't know what you are talking about....Of course if the wall is flimsy and weak, then this is probably not a good solution.

I've laid - and demolished - enough brick and block to have a fair idea. And on ONE occasion , dropped about eight feet of non-load-bearing brick wall with a SINGLE swing of a 12 pound sledge. It seldom takes more than a dozen. 'Common' brick has high compressive strength - and damn little else. And walls are seldom built of furnace brick, which is a whole 'nuther animal.

More on-point though, the situation the OP has is a brick wall he cannot see all of the quality of. The back side? Maybe. The 'front'? Certainly not

For the sake of safety, one HAS TO assume the worst - eg: 'flimsy and weak'. Mortar-Forkers seldom do a brick wall with tightly fitted and pointed type-S mortar work if they expect it to be covered-up. Bloody lucky to get even good type-N.

And folk who encounter an existing brick wall they think is best covered up were probably not looking at a particularly well-laid wall, either.

Don't risk it. The brick AND the mortar are highly frangible, and the joints are just not up for that sort of impact. Save the bush hammer for proper concrete.

Bill

A scutch hammer or chisel would be the correct tool for render removal over here. A light circa sub 2lb hammer with replaceable cutting blades, used like a Adze is on wood work. They work great in a SDS drill with roto stop too. Light blows applied in quick succession inline with the brick - render bond line.

By the very nature of a brick wall a load bearing one can not be knocked down in its entirety with one hammer blow if its in a normal state of repair. The greater the loading, the stronger the bricks are held. No load and a light breeze can easily blow them over. The mortar, is not there as a glue to stick the bricks together, more a sort of gasket compound, to seal out the weather and a grout to spread the load evenly on the uneven bricks.